When I close my eye, I usually see an outline of bright/dark somewhat matching what I last saw, but desaturated and splotchy.
If I keep my eyes close, the patches kinda drift around. It's kinda fun to watch sometimes but I get bored eventually open my eyes.
I've always assumed its my eyes just adjusting to the dark, or maybe its residual light my eyelids can't filter out.
This following link discusses the phenomenon in terms of phosphenes:
https://www.huffpost.com/entry/why-do-i-see-patterns-when-i-...
Arguably, there have been spiritual movements fueled by relative ignorace around these things, with gurus allegedly claiming that they enable these unexpected experiences for their disciples.
I can voluntarily cause a burst of those color patterns by, after closing my eyes, relaxing all my facial muscles and letting my eyes go unfocused. Works best when trying to fall asleep, so I can imagine people unintentionally doing the same during, say, meditation and correlating it with their spiritual leader.
A sociologist who studied the spiritual cultures concluded there were many conformity-related behaviors at work. Oh, yea, I had the experience.